3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
The 3GPP LTE-A employs various techniques such as carrier aggregation, relay, etc. The 3GPP LTE system is a single carrier system supporting only one bandwidth (i.e., one component carrier) among {1.4, 3, 5, 10, 15, 20}MHz. On the other hand, the LTE-A employs multiple carriers using carrier aggregation. The component carrier is defined with a center frequency and a bandwidth.
The component carrier may correspond to one cell. A multiple carrier system uses a plurality of component carriers having a narrower bandwidth than a full bandwidth.
With the introduction of the multiple carrier system, the user equipment (UE) can receive a service from a plurality of cells. However, battery consumption of the UE may increase to maintain a connection with the plurality of cells.
It is not always necessary for the UE to receive the service from a fixed number of cells. Accordingly, there is a need to dynamically activate or inactivate a cell in order to reduce the battery consumption of the UE.